1. Field of the Invention
The present invention relates to a surface texture measuring apparatus. More specifically, the present invention relates to a surface texture measuring apparatus capable of keeping a measuring force constant regardless of a posture of a measurement arm having a stylus that makes contact with a surface of a measured object.
2. Description of Related Art
A surface texture measuring apparatus is known which moves a stylus in contact with a surface of a measured object along the surface thereof, detects a displacement of the stylus (displacement in a direction orthogonal to a travel direction of the stylus) generated at this point due to a shape and roughness of the surface of the measured object, and, from the displacement, measures a surface texture such as the shape and roughness of the surface of the measured object.
Among the surface texture measuring apparatuses, a type of surface texture measuring apparatus has been suggested which pre-prepares styli (measurement arms) of various shapes so as to enable measurement on various shapes of measured portions in a measured object, and performs measurement while switching styli to those which are most appropriate for the shape of the measured portion of the measured object. The surface texture measuring apparatus is further capable of tilting a detector main body including the stylus (measurement arm) so as to enable measurement on an inclined surface of the measured object. In addition, the surface texture measuring apparatus can automatically adjust a measurement force to be appropriate for a combination of a stylus and a measured surface.
For example, Japanese Patent No. 3992853 describes a technology in which a measurement force command value is pre-stored in a table for each combination of a stylus holder type, a stylus type, a measurement direction, and an inclination angle of the detector main body; a user specifies the stylus holder type, the stylus type, and the measurement direction when a stylus holder or a stylus is changed; a measurement force command value corresponding to the specifications and the inclination angle of the detector main body detected by an angle detector is read out from the table; and the measurement force is automatically adjusted according to the read-out measurement force command value.
Thus, it is possible to adjust a measurement force to be most appropriate for the measurement direction (upward or downward, for example) and the inclination angle of the main body in addition to the combination of the stylus holder type and the stylus type. In other words, it is possible to adjust a measurement force to be a predetermined level even when a stylus or a holder is changed, or a measurement direction or an angle is changed.
The technology described in Japanese Patent No. 3992853, however, needs to convert to a table and store in a memory, in advance, each measurement force command value for each combination of the stylus holder type, the stylus type, and the inclination angle of the detector main body. Depending on a shape of the measured object, there may be a desire to use an apparatus with an inclination angle other than that stored in the table. In such a case, the technology described in Japanese Patent No. 3992853 cannot perform accurate measurement because a measurement force command value for the desired inclination angle is not stored.
In addition, when an inclination angle for the detector main body is allowed to be finely specified, required memory capacity is significantly increased. Further, when a user wants to use an unregistered stylus, the user needs to obtain a measurement force command value for the new stylus that the user wants to use, the stylus holder type, the measurement direction, and the inclination angle, which increases the user's workload.
An advantage of the present invention is to provide a surface texture measuring apparatus capable of performing accurate measurement even when an inclination angle of a detector displacement mechanism is changed to a predetermined angle, while achieving a smaller memory capacity and reducing a workload for a user even when use of a new stylus is desired.